Field of the Invention
This invention relates to the art of prosthetic devices and methods for implanting the devices between adjacent vertebrae to treat or prevent back pain in patients with ruptured or degenerated intervertebral discs. Specifically this invention deals with improvements in prosthetic strut forming plugs or blocks with roughened surfaces facilitating bone ingrowth from adjoining vertebrae wherein the blocks are shaped to fit in rectangular slots cut in the vertebrae, have heights which will stretch the remaining elastic annulus tissues of damaged discs between the adjoining vertebrae and have slots extending vertically, transversely or both vertically and transversely through the plugs to be packed with bone grafts to expedite the bone ingrowth.
More specifically the plugs or blocks fitting the rectangular slots in the adjoining vertebrae have tapered leading ends facilitating insertion into the slots between the vertebrae to stretch remaining disc tissue connecting the vertebrae and tool receiving trailing ends for forcing the plugs into position. A still further specific feature of the invention is the provision of plugs which are radiolucent for improved X-ray visualization of the bone healing post-operatively.
As pointed out in my aforesaid parent U.S. Pat. No. 4,743,256 its continuation-in-part application Ser. No. 095,461, the leading cause of low back pain arises from rupture or degeneration of lumbar intervertebral discs. Pain in the lower extremities of the back (sciatica) is caused by the compression of spinal nerve roots by damaged discs between the vertebrae and low back pain is caused by collapse of the disc and the adverse effects of bearing the majority of the body weight through a damaged unstable vertebrae joint. Surgical treatments for relief of the sciatic pain and lower back pain generally include the following: